It doesn't make that much sense though. Who do gang members kill more than anyone else? Other gang members. Does that make them good people, since they are killing other bad people?
The Fiends kill people solely for entertainment, meat, sadistic pleasure, forced intimacy or money.
They don't care about anyone.
They'd slit your throat for 10 caps just so they could get a fix.
They are in now way good people or "misunderstood".
I know that The Legion seems like sadistic [censored]s as well but at least they have a goal for doing what they do.
They might be considered evil at the moment but what if they won and restored peace to the wasteland in a century or two?
It would make all "evil" things they did in the past worth it cause because of what they did something good came out of it.
So it's left open to the player whether or not to consider them good or evil.
But give one example where Fiends can be considered good people?